Mobile terminal including wireless charging module and battery pack

ABSTRACT

A mobile terminal is provided, which includes a wireless charging module, a battery pack, and a circuit board substrate. The wireless charging module includes a charging coil formed of a wound conducting wire and a communication coil placed adjacent to the charging coil. The wireless charging module has a substantially planar shape. The battery pack has a substantially planar shape and is configured to store power from the wireless charging module. The circuit board substrate is configured to control operation of the mobile terminal. The wireless charging module overlaps with each of the circuit board substrate and the battery pack.

BACKGROUND Technical Field

The present invention relates to a wireless charging module including awireless charging module and an NFC antenna, as well as a portableterminal that includes the wireless charging module.

Description of the Related Art

In recent years, NFC (Near Field Communication) antennas that utilizeRFID (Radio Frequency IDentification) technology and use radio waves inthe 13.56 MHz band and the like are being used as antennas that aremounted in communication apparatuses such as portable terminal devices.To improve the communication efficiency, an NFC antenna is provided witha magnetic sheet that improves the communication efficiency in the 13.56MHz band and thus configured as an NFC antenna module. Technology hasalso been proposed in which a wireless charging module is mounted in acommunication apparatus, and the communication apparatus is charged bywireless charging. According to this technology, a power transmissioncoil is disposed on the charger side and a power reception coil isprovided on the communication apparatus side, electromagnetic inductionis generated between the two coils at a frequency in a band betweenapproximately 100 kHz and 200 kHz to thereby transfer electric powerfrom the charger to the communication apparatus side. To improve thecommunication efficiency, the wireless charging module is also providedwith a magnetic sheet that improves the efficiency of communication inthe band between approximately 100 kHz and 200 kHz.

Portable terminals that include such NFC modules and wireless chargingmodules have also been proposed (for example, see PTL 1).

CITATION LIST Patent Literature

PTL 1

Japanese Patent No. 4669560

BRIEF SUMMARY

A mobile terminal is provided, which includes a wireless chargingmodule, a battery pack, and a circuit board substrate. The wirelesscharging module includes a charging coil formed of a wound conductingwire and a communication coil placed adjacent to the charging coil. Thewireless charging module has a substantially planar shape. The batterypack has a substantially planar shape and is configured to store powerfrom the wireless charging module. The circuit board substrate isconfigured to control operation of the mobile terminal. The wirelesscharging module overlaps with each of the circuit board substrate andthe battery pack.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams illustrating a wireless chargingmodule according to an embodiment of the present invention;

FIGS. 2A and 2B are schematic diagrams illustrating a charging coil anda magnetic sheet according to the embodiment of the present invention;

FIGS. 3A to 3D illustrate relations between a primary-side wirelesscharging module that includes a magnet, and a charging coil according tothe embodiment of the present invention;

FIG. 4 illustrates a relation between the size of an inner diameter of ahollow portion of a charging coil and an L value of the charging coilwhen an outer diameter of the hollow portion of the charging coil iskept constant with respect to a case where a magnet is provided in aprimary-side wireless charging module and a case where a magnet is notprovided therein;

FIG. 5 illustrates a relation between an L value of a charging coil anda percentage of hollowing of a center portion with respect to a casewhere a magnet is provided in a primary-side wireless charging moduleand a case where a magnet is not provided therein;

FIG. 6 is a perspective view when the NFC coil and the magnetic bodyaccording to the present embodiment have been assembled;

FIG. 7 is an exploded view illustrating the arrangement of the NFC coiland the magnetic body according to the present embodiment;

FIGS. 8A and 8B illustrate the wiring of the NFC coil according to thepresent embodiment;

FIG. 9 is a conceptual diagram showing an antenna apparatus formed by anelectronic circuit board and an NFC coil that are mounted in a portableterminal according to the present embodiment, and lines of magneticforce generated from the antenna apparatus;

FIGS. 10A and 10B are schematic diagrams of lines of magnetic force thata charging coil and NFC coils generate according to the presentembodiment;

FIGS. 11A and 11B are perspective views illustrating a portable terminalequipped with the wireless charging module according to the presentembodiment, and a portable terminal equipped with a wireless chargingmodule that includes a loop-shaped NFC antenna for comparison;

FIG. 12 illustrates a frequency characteristic of an induced voltage foreach of the two wireless charging modules illustrated in FIGS. 11A and11B;

FIGS. 13A and 13B each illustrate a magnetic field on a YZ plane of acorresponding one of the two wireless charging modules illustrated inFIGS. 11A and 11B;

FIGS. 14A and 14B each illustrate a magnetic field on a ZX plane of acorresponding one of the two wireless charging modules illustrated inFIGS. 11A and 11B; and

FIGS. 15A to 15E are sectional views that schematically illustrate aportable terminal including the wireless charging module according tothe present embodiment.

DETAILED DESCRIPTION

The invention of the present disclosure can obtain a wireless chargingmodule that includes a charging coil formed of a wound conducting wire,and an NFC coil that is placed around the charging coil, in which anaxis of the charging coil and a winding axis of the NFC coil intersectwith each other. The wireless charging module achieves a reduction insize by making a wireless charging coil and an NFC antenna into a singlemodule, and enables communication and power transmission in the samedirection while also making coil axis directions of antennas differentfrom each other to prevent mutual interference.

In the wireless charging module of the present disclosure, the axis ofthe charging coil and the axis of the NFC coil are substantiallyorthogonal to each other. Thus, mutual interference can be prevented themost.

In the wireless charging module of the present disclosure, the wirelesscharging module comprises a plurality of the NFC coils, in which theplurality of NFC modules are placed so as to sandwich the wirelesscharging module between the plurality of NFC modules. Thus, mutualinterference can be prevented while a reduction in size is achieved.

Further, in the wireless charging module of the present disclosure: thecharging coil is wound in a substantially rectangular shape; and atleast two of the NFC coils are placed along two facing sides of thecharging coil of the rectangular shape. Thus, a region in which NFCcommunication is possible can be widened with favorable balance aroundthe wireless charging module.

The wireless charging module of the present disclosure further includesa magnetic sheet including a face on which the charging coil is to beentirely mounted, in which the NFC coil is placed outside the magneticsheet. Thus, communication of the NFC coil can be performed efficiently.

The wireless charging module of the present disclosure further includesa magnetic sheet including a face on which the charging coil is to beentirely mounted, wherein the NFC coil is wound around a magnetic core.Thus, the thickness and size of the entire wireless charging module canbe reduced while a large opening portion of the charging coil thattransmits a large amount of power over a short range can be secured.

Further, in the wireless charging module of the present disclosure, themagnetic sheet and the magnetic core are formed of different materialsfrom each other. Thus, objective effects can be improved by using amagnetic material that is suitable for the charging coil that transmitsa large amount of power over a short range and a magnetic material thatis suitable for the NFC coil that communicates by transmitting a smallamount of power over a long range, respectively.

In the wireless charging module of the present disclosure, the magneticsheet and the magnetic core are formed of different kinds of ferritefrom each other. Thus, objective effects can be dramatically improved byusing a ferrite material that is suitable for the charging coil thattransmits a large amount of power over a short range and a ferritematerial that is suitable for the NFC coil that communicates bytransmitting a small amount of power over a long range.

In the wireless charging module of the present disclosure, the overallthickness in a stacking direction of the charging coil and the magneticsheet is greater than a thickness of the NFC coil in a directionidentical to the stacking direction. Thus, an overall reduction in sizeand in thickness can be effectively realized by forming the NFC coilthat is placed on the outside with a reduced thickness.

Further, in the wireless charging module of the present disclosure, alength in a longitudinal direction of the two facing sides of therectangular charging coil is shorter than a length of the NFC coil in adirection identical to the longitudinal direction. Thus, it is difficultfor a situation to arise in which the charging coil interferes with amagnetic field that the NFC coil generates.

In the wireless charging module of the present disclosure, a number ofturns of the charging coil is greater than a number of turns of the NFCcoil. Thus, an inductance value of the charging coil that transmits alarger amount of power can be increased.

In the wireless charging module of the present disclosure, an openingarea of the charging coil is larger than an opening area of the NFCcoil. Thus, an inductance value of the charging coil that transmits alarger amount of power can be increased.

In the wireless charging module of the present disclosure, the numbersof turns of the plurality of NFC coils are equal to each other. Thus, amagnetic field is generated with favorable balance from the plurality ofNFC coils, and hence NFC communication can be stably performed.

Further, in the wireless charging module of the present disclosure, theplurality of NFC coils are an identical shape. Thus, a magnetic field isgenerated with favorable balance from the plurality of NFC coils, andhence NFC communication can be stably performed.

In addition, a portable terminal of the present disclosure includes thewireless charging module of the present disclosure inside a casing.Thus, it is possible to obtain a wireless charging module that achievesa reduction in size by making a wireless charging coil and an NFCantenna into a single module and enables communication and powertransmission in the same direction while also making coil axisdirections of antennas different from each other to prevent mutualinterference.

In the portable terminal of the present disclosure, a metal body isprovided inside the casing and the NFC coil is placed at an edge of themetal body. Thus, a magnetic field that the NFC antenna generates can becaused to incline and NFC communication can be performed moreefficiently.

Further, in the portable terminal of the present disclosure, an openingportion of the NFC coil is substantially perpendicular to the metalbody. Thus, an eddy current with respect to the NFC antenna that arisesinside the metal body can be suppressed, and NFC communication can beperformed more efficiently.

Embodiment

[Regarding Wireless Charging Module]

Hereunder, an overview of a wireless charging module according to anembodiment of the present invention will be described using FIGS. 1A and1B. FIGS. 1A and 1B are schematic diagrams illustrating a wirelesscharging module according to an embodiment of the present invention.FIG. 1A is a top view of the wireless charging module, and FIG. 1B is aperspective view of the wireless charging module.

Wireless charging module 100 of the present embodiment includes:charging coil 30 that includes a conducting wire wound in a planarshape; two NFC coils 40 that are placed around charging coil 30; andmagnetic sheet 10 that supports charging coil 30. The number of NFCcoils 40 provided in wireless charging module 100 may also be one,three, four or more.

Wireless charging module 100 includes sheet-like magnetic sheet 10 thatincludes an upper face and a lower face in an opposite direction.Charging coil 30 is mounted (adhered) on the upper face of magneticsheet 10. At least one NFC coil 40, and preferably a plurality of NFCcoils 40 are placed around magnetic sheet 10 and charging coil 30. Inthe present embodiment, two NFC coils 40 are provided that face eachother with magnetic sheet 10 and charging coil 30 sandwichedtherebetween. NFC coils 40 may also be mounted on the upper face ofmagnetic sheet 10. The coil axes of the two NFC coils 40 aresubstantially parallel to each other (the coil axes may also intersectat an angle between around −10 to +10 degrees), and the coil axes may bein a relation in which the coil axes are substantially perpendicular orinclined with respect to each other. It is favorable to wind NFC coil 40around magnetic body 20, since the communication efficiency of NFC coil40 is improved thereby. The area of an upper face of single magneticbody 20 is smaller than the area of the upper face of magnetic sheet 10.Coil axis

A of charging coil 30 and coil axis B of NFC coil 40 intersect with eachother in a substantially orthogonal manner (at an angle betweenapproximately 75 and 105 degrees). Although in the present embodimentmagnetic sheet 10 and magnetic body 20 come in contact through aprotective tape or the like, magnetic sheet 10 and magnetic body 20 maybe separated from each other. By making magnetic sheet 10 and magneticbody 20 contact, magnetic sheet 10 and magnetic body 20 can beconfigured to the maximum size inside wireless charging module 100 thatis reduced in size.

[Regarding Charging Coil]

The charging coil will be described in detail using FIGS. 2A and 2B.

FIGS. 2A and 2B are schematic diagrams of a charging coil and a magneticsheet according to the embodiment of the present invention. FIG. 2A isan exploded view illustrating the arrangement relationship between thecharging coil and the magnetic sheet. FIG. 2B is a top view of thecharging coil and the magnetic sheet.

In the present embodiment, charging coil 30 is wound in a substantiallysquare shape, but may be wound in any shape such as a substantiallyrectangular shape including a substantially oblong shape, a circularshape, an elliptical shape, and a polygonal shape.

Charging coil 30 has two leg portions (terminals) 32 a and 32 b as astarting end and a terminating end thereof, and includes a litz wireconstituted by around 8 to 15 conducting wires having a diameter ofapproximately 0.1 mm or a plurality of wires (preferably, around 2 to 15conducting wires having a diameter of 0.08 mm to 0.3 mm) that is woundaround a hollow portion as though to draw a swirl on the surface. Forexample, in the case of a coil including a wound litz wire made of 12conducting wires having a diameter of 0.1 mm, in comparison to a coilincluding a single wound conducting wire having the same cross-sectionalarea, the alternating-current resistance decreases considerably due tothe skin effect. If the alternating-current resistance decreases whilethe coil is operating, heat generation by the coil decreases and thuscharging coil 30 that has favorable thermal properties can be realized.At this time, if a litz wire that includes 8 to 15 conducting wireshaving a diameter of 0.08 mm to 1.5 mm is used, favorable power transferefficiency can be achieved. If a single wire is used, it is advantageousto use a conducting wire having a diameter between 0.2 mm and 1 mm.Further, for example, a configuration may also be adopted, in which,similarly to a litz wire, a single conducting wire is formed of threeconducting wires having a diameter of 0.2 mm and two conducting wireshaving a diameter of 0.3 mm. Leg portions 32 a and 32 b as a currentsupply section supply a current from a commercial power source that isan external power source to charging coil 30. Note that an amount ofcurrent that flows through charging coil 30 is between approximately 0.4A and 2 A. In the present embodiment the amount of current is 0.7 A.

In charging coil 30 of the present embodiment, a distance between facingsides (a length of one side) of the hollow portion having asubstantially square shape is 20 mm (between 15 mm and 25 mm ispreferable), and a distance between facing sides (a length of one side)at an outer edge of the substantially square shape is 30 mm (between 25mm and 45 mm is preferable). Charging coil 30 is wound in a donut shape.In a case where charging coil 30 is wound in a substantially oblongshape, with respect to facing sides of the hollow portion of thesubstantially oblong shape, a distance between short sides (a length ofone side) is 15 mm (between 10 mm and 20 mm is preferable) and adistance between long sides (a length of one side) is 23 mm (between 15mm and 30 mm is preferable). Further, with respect to facing sides at anouter edge of a substantially square shape, a distance between shortsides (a length of one side) is 28 mm (between 15 mm and 35 mm ispreferable) and a distance between long sides (a length of one side) is36 mm (between 20 mm and 45 mm is preferable). In a case where chargingcoil 30 is wound in a circular shape, the diameter of the hollow portionis 20 mm (between 10 mm and 25 mm is preferable) and the diameter of anouter edge of the circular shape is 35 mm (between 25 mm and 45 mm ispreferable). Note that, the combined thickness of charging coil 30 andmagnetic sheet 10 in a state in which charging coil 30 is stacked onmagnetic sheet 10 is 0.8 mm. To achieve a reduction in the thickness ofthe module, it is preferable that the combined thickness of chargingcoil 30 and magnetic sheet 10 is between 0.6 mm and 1 mm.

In some cases charging coil 30 is the secondary side (power receptionside), and utilizes a magnet for alignment with a coil of a primary-sidewireless charging module inside a charger that supplies power tocharging coil 30 as a counterpart for power transmission. A magnet insuch a case is defined by the standard (WPC) as a circular (coin shaped)neodymium magnet having a diameter of approximately 15.5 mm(approximately 10 mm to 20 mm) and a thickness of approximately 1.5 mmto 2 mm or the like. A favorable strength of the magnet is approximately75 mT to 150 mT. Since an interval between a coil of the primary-sidewireless charging module and charging coil 30 is around 2 to 5 mm, it ispossible to adequately perform alignment using such a magnet. The magnetis disposed in a hollow portion of the wireless charging module coil onthe primary side or secondary side. In the present embodiment, themagnet is disposed in the hollow portion of charging coil 30.

That is, for example, the following methods may be mentioned as analigning method. For example, a method is available in which aprotruding portion is formed in a charging surface of a charger, arecessed portion is formed in an electronic device on the secondaryside, and the protruding portion is fitted into the recessed portion tothereby physically (geometrically) perform compulsory aligning. A methodis also available in which a magnet is mounted on at least one of theprimary side and secondary side, and alignment is performed byattraction between the respective magnets or between a magnet on oneside and a magnetic sheet on the other side. According to anothermethod, the primary side detects the position of a coil of the secondaryside and automatically moves a coil on the primary side to the positionof the coil on the secondary side. Other available methods include amethod in which a large number of coils are provided in a charger sothat a portable device can be charged at every place on the chargingsurface of the charger.

Thus, various methods can be mentioned as common methods for aligningthe coils of the primary-side (charging-side) wireless charging moduleand the secondary-side (charged-side) wireless charging module, and themethods are divided into methods that use a magnet and methods that donot use a magnet. By configuring wireless charging module 100 to beadaptable to both a primary-side (charging-side) wireless chargingmodule that uses a magnet and a primary-side wireless charging modulethat does not use a magnet, charging can be performed regardless of thetype of primary-side wireless charging module, which in turn improvesthe convenience of the module.

The influence that a magnet has on the power transmission efficiency ofwireless charging module 100 will be described.

When magnetic flux for electromagnetic induction is generated betweenthe primary-side wireless charging module and wireless charging module100 to transmit power, the presence of a magnet between or around theprimary-side wireless charging module and wireless charging module 100leads extension of the magnetic flux to avoid the magnet. Otherwise, themagnetic flux that passes through the magnet becomes an eddy current orgenerates heat in the magnet and is lost. Furthermore, if the magnet isdisposed in the vicinity of magnetic sheet 10, magnetic sheet 10 that isin the vicinity of the magnet saturates and the magnetic permeabilitythereof decreases. Therefore, the magnet that is included in theprimary-side wireless charging module may decrease an L value ofcharging coil 30. As a result, transmission efficiency between thewireless charging modules will decrease. To prevent this, in the presentembodiment the hollow portion of charging coil 30 is made larger thanthe magnet. That is, the area of the hollow portion is made larger thanthe area of a circular face of the coin-shaped magnet, and an insideedge (portion surrounding the hollow portion) of charging coil 30 isconfigured to be located at a position that is on the outer siderelative to the outer edge of the magnet. Further, because the diameterof the magnet is 15.5 mm or less, it is sufficient to make the hollowportion larger than a circle having a diameter of 15.5 mm. As anothermethod, charging coil 30 may be wound in a substantially oblong shape(including a square shape), and a diagonal of the hollow portion havinga substantially oblong shape may be made longer than the diameter(maximum 15.5 mm) of the magnet. As a result, since the corner portions(four corners) at which the magnetic flux concentrates of charging coil30 that is wound in a substantially oblong shape are positioned on theouter side relative to the magnet, the influence of the magnet can besuppressed. Effects obtained by employing the above describedconfiguration are described hereunder.

FIGS. 3A to 3D illustrate relations between the primary-side wirelesscharging module including the magnet, and the charging coil according tothe embodiment of the present invention. FIG. 3A illustrates a casewhere the aligning magnet is used when the inner width of the woundcharging coil is small. FIG. 3B illustrates a case where the aligningmagnet is used when the inner width of the wound charging coil is large.FIG. 3C illustrates a case where the aligning magnet is not used whenthe inner width of the wound charging coil is small. FIG. 3D illustratesa case where the aligning magnet is not used when the inner width of thewound charging coil is large.

Primary-side wireless charging module 200 that is disposed inside thecharger includes primary-side coil 210, magnet 220, and a magnetic sheet(not illustrated in the drawings). In FIGS. 3A to 3D, magnetic sheet 10,charging coil 30, and NFC coil 40 inside wireless charging module 100are schematically illustrated.

Wireless charging module 100 and primary-side wireless charging module200 are aligned so that primary-side coil 210 and charging coil 30 faceeach other. A magnetic field is generated between inner portion 211 ofprimary-side coil 210 and inner portion 33 of charging coil 30 and poweris transmitted. Inner portion 211 and inner portion 33 face each other.Inner portion 211 and inner portion 33 are close to magnet 220 and areliable to be adversely affected by magnet 220.

In addition, because magnet 220 is disposed in the vicinity of magneticsheet 10 and magnetic body 20, the magnetic permeability of magneticsheet 10 in the vicinity of magnet 220 decreases. Naturally, magneticsheet 10 is closer than magnetic body 20 to magnet 220, and is moreliable to be affected by magnet 220. Therefore, magnet 220 included inprimary-side wireless charging module 200 weakens the magnetic flux ofprimary-side coil 210 and charging coil 30, particularly, at innerportion 211 and inner portion 33, and exerts an adverse effect. As aresult, the transmission efficiency of the wireless charging decreases.Accordingly, in the case illustrated in FIG. 3A, inner portion 33 thatis liable to be adversely affected by magnet 220 is large.

In contrast, in the case illustrated in FIG. 3C in which a magnet is notused, the L value increases because the number of turns of charging coil30 is large. As a result, since there is a significant decrease in thenumerical value from the L value in FIG. 3C to the L value in FIG. 3A,when using a wound coil having a small inner width, the L-value decreaserate with respect to an L value in a case where magnet 220 is includedfor alignment and an L value in a case where magnet 220 is not includedis extremely large.

Further, if the inner width of charging coil 30 is smaller than thediameter of magnet 220 as illustrated in FIG. 3A, charging coil 30 isdirectly adversely affected by magnet 220 to a degree that correspondsto the area of charging coil 30 that faces magnet 220. Accordingly, itis better for the inner width of charging coil 30 to be larger than thediameter of magnet 220.

In contrast, when the inner width of charging coil 30 is large asillustrated in FIG. 3B, inner portion 33 that is liable to be adverselyaffected by magnet 220 is extremely small. In the case illustrated inFIG. 3D in which magnet 220 is not used, the L value is smaller than inFIG. 3C because the number of turns of charging coil 30 is less. Thus,because a decrease in the numerical value from the L value in the caseillustrated in FIG. 3D to the L value in the case illustrated in FIG. 3Bis small, the L-value decrease rate can be suppressed to a small amountin the case of coils that have a large inner width. Further, as theinner width of charging coil 30 increases, the influence of magnet 220can be suppressed because the distance from magnet 220 to the edge ofthe hollow portion of charging coil 30 increases.

On the other hand, since wireless charging module 100 is mounted in anelectronic device or the like, charging coil 30 cannot be made largerthan a certain size. Accordingly, if the inner width of charging coil 30is enlarged to reduce the adverse effects from magnet 220, the number ofturns will decrease and the L value itself will decrease regardless ofthe presence or absence of magnet 220. Therefore, since magnet 220 canbe made the maximum size in a case where the area of magnet 220 and thearea of the hollow portion of charging coil 30 are substantially thesame (the outer diameter of magnet 220 is about 0 to 2 mm smaller thanthe inner width of charging coil 30, or the area of magnet 220 is aproportion of about 75% to 95% relative to the area of the hollowportion of charging coil 30), the alignment accuracy between theprimary-side wireless charging module and the secondary-side wirelesscharging module can be improved. Further, if the area of magnet 220 isless than the area of the hollow portion of charging coil 30 (the outerdiameter of magnet 220 is about 2 to 8 mm smaller than the inner widthof charging coil 30, or the area of magnet 220 is a proportion of about45% to 75% relative to the area of the hollow portion of charging coil30), even if there are variations in the alignment accuracy, it ispossible to ensure that magnet 220 is not present at a portion at whichinner portion 211 and inner portion 33 face each other.

In addition, as charging coil 30 that is mounted in wireless chargingmodule 100 having the same lateral width and vertical width, theinfluence of magnet 220 can be suppressed more by winding the coil in asubstantially rectangular shape rather than in a circular shape. Thatis, comparing a circular coil in which the diameter of a hollow portionis represented by “x” and a substantially square coil in which adistance between facing sides of the hollow portion (a length of oneside) is represented by “x,” if conducting wires having the samediameter as each other are wound with the same number of turns, therespective conducting wires will be housed in respective wirelesscharging modules 100 that have the same width. In such case, length y ofa diagonal of the hollow portion of the substantially square-shaped coilwill be such that y>x. Accordingly, if the diameter of magnet 220 istaken as “m,” a distance (x−m) between the innermost edge of thecircular coil and magnet 220 is always constant (x>m). On the otherhand, a distance between the innermost edge of a substantiallyrectangular coil and magnet 220 is a minimum of (x−m), and is a maximumof (y−m) at corner portions 31 a to 31 d. When charging coil 30 includescorners such as corner portions 31 a to 31 d, magnetic flux concentratesat the corners during power transmission. That is, corner portions 31 ato 31 d at which the most magnetic flux concentrates are furthest frommagnet 220, and moreover, the width (size) of wireless charging module100 does not change. Accordingly, the power transmission efficiency ofcharging coil 30 can be improved without making wireless charging module100 a large size.

The size of charging coil 30 can be reduced further if charging coil 30is wound in a substantially oblong shape. That is, even if a short sideof a hollow portion that is a substantially oblong shape is smaller thanm, as long as a long side thereof is larger than m it is possible todispose four corner portions outside of the outer circumference ofmagnet 220. Accordingly, when charging coil 30 is wound in asubstantially oblong shape around a hollow portion having asubstantially oblong shape, charging coil 30 can be wound in a favorablemanner as long as at least the long side of the hollow portion is largerthan m. Note that, the foregoing description of a configuration in whichthe innermost edge of charging coil 30 is on the outer side of magnet220 that is provided in primary-side wireless charging module 200 and inwhich four corners of the substantially rectangular hollow portion ofcharging coil 30 that is wound in a substantially rectangular shape areon the outside of magnet 220 refers to a configuration as shown in FIG.3B. That is, the foregoing describes a fact that when an edge of thecircular face of magnet 220 is extended in the stacking direction andcaused to extend as far as wireless charging module 100, a regionsurrounded by the extension line is contained within the hollow portionof charging coil 30.

FIG. 4 illustrates a relation between the size of the inner diameter ofthe wound charging coil and the L value of the charging coil when theouter diameter of the wound charging coil is kept constant, with respectto a case where a magnet is provided in the primary-side wirelesscharging module and a case where the magnet is not provided therein. Asshown in FIG. 4, when the size of magnet 220 and the outer diameter ofcharging coil 30 are kept constant, the influence of magnet 220 oncharging coil 30 decreases as the number of turns of charging coil 30decreases and the inner diameter of charging coil 30 increases. That is,the L value of charging coil 30 in a case where magnet 220 is utilizedfor alignment between primary-side wireless charging module 200 and(secondary-side) wireless charging module 100 and the L value ofcharging coil 30 in a case where magnet 220 is not utilized foralignment approach each other. Accordingly, a resonance frequency whenmagnet 220 is used and a resonance frequency when magnet 220 is not usedbecome extremely similar values. At such time, the outer diameter of thewound coil is uniformly set to 30 mm. Further, by making the distancebetween the edge of the hollow portion of charging coil 30 (innermostedge of charging coil 30) and the outer edge of magnet 220 greater than0 mm and less than 6 mm, the L values in the case of utilizing magnet220 and the case of not utilizing magnet 220 can be made similar to eachother while maintaining the L values at 15 μH or more.

The conducting wire of charging coil 30 may be a single conducting wirethat is stacked in a plurality of stages, and the stacking direction inthis case is the same as the stacking direction in which magnetic sheet10 and charging coil 30 are stacked. At such time, by stacking thelayers of conducting wire that are arranged in the vertical directionwith a space interposed in between, stray capacitance between conductingwire on an upper stage and conducting wire on a lower stage decreases,and the alternating-current resistance of charging coil 30 can besuppressed to a small amount. Further, the thickness of charging coil 30can be minimized by winding the conducting wire densely. By stacking theconducting wire in this manner, the number of turns of charging coil 30can be increased to thereby improve the L value. However, in comparisonto winding of charging coil 30 in a plurality of stages in the stackingdirection, winding of charging coil 30 in one stage can lower thealternating-current resistance of charging coil 30 and raise thetransmission efficiency.

If charging coil 30 is wound in a polygonal shape, corner portions(corners) 31 a to 31 d are provided as described below. Charging coil 30that is wound in a substantially square shape refers to a coil in whichR (radius of a curve at the four corners) of corner portions 31 a to 31d that are four corners of the hollow portion is equal to or less than30% of the edge width of the hollow portion. That is, in FIG. 2B, in thesubstantially square hollow portion, the four corners have a curvedshape. In comparison to right angled corners, the strength of theconducting wire at the four corners can be improved when the corners arecurved to some extent. However, if R is too large, there is almost nodifference from a circular coil and it will not be possible to obtaineffects that are only obtained with a substantially square charging coil30. It has been found that when the edge width of the hollow portion is,for example, 20 mm, and radius R of a curve at each of the four cornersis 6 mm or less, the influence of magnet 220 can be effectivelysuppressed. Further, when taking into account the strength of the fourcorners as described above, the greatest effect of the rectangular coildescribed above can be obtained by making radius R of a curve at each ofthe four corners an amount that corresponds to a proportion of 5 to 30%relative to the edge width of the substantially square hollow portion.Note that, even in the case of charging coil 30 wound in a substantiallyoblong shape, the effect of the substantially oblong coil describedabove can be obtained by making radius R of a curve at each of the fourcorners an amount that corresponds to a proportion of 5 to 30% relativeto the edge width (either one of a short side and a long side) of thesubstantially oblong hollow portion. Note that, in the presentembodiment, with respect to the four corners at the innermost end(hollow portion) of charging coil 30, R is 2 mm, and a preferable valuefor R is between 0.5 mm and 4 mm.

Further, when winding charging coil 30 in a rectangular shape,preferably, leg portions 32 a and 32 b are provided in the vicinity ofcorner portions 31 a to 31 d. When charging coil 30 is wound in acircular shape, irrespective of where leg portions 32 a and 32 b areprovided, leg portions 32 a and 32 b can be provided at a portion atwhich a planar coil portion is wound in a curve. When the conductingwire is wound in a curved shape, a force acts that tries to maintain thecurved shape thereof, and it is difficult for the overall shape to bebroken even if leg portions 32 a and 32 b are formed. In contrast, inthe case of a coil in which the conducting wire is wound in arectangular shape, there is a difference in the force with which thecoil tries to maintain the shape of the coil itself with respect to sideportions (linear portions) and corner portions. That is, at cornerportions 31 a to 31 d in FIG. 2B, a large force acts to try to maintainthe shape of charging coil 30. However, at each side portion, a forcethat acts to try to maintain the shape of charging coil 30 is small, andthe conducting wire is liable to become uncoiled from charging coil 30in a manner in which the conducting wire pivots around the curves atcorner portions 31 a to 31 d. As a result, the number of turns ofcharging coil 30 fluctuates by, for example, about ⅛ turn, and the Lvalue of charging coil 30 fluctuates. That is, the L value of chargingcoil 30 varies. Accordingly, it is favorable for a winding start pointon leg portion 32 a side of the conducting wire to be adjacent to cornerportion 31 a, and for the conducting wire to bend at corner portion 31 aimmediately after the winding start point. The winding start point andcorner portion 31 a may also be adjacent. Subsequently, the conductingwire is wound a plurality of times until a winding end point is formedbefore bending at corner portion 31 a, and the conducting wire thenforms leg portion 32 b and is bent to the outer side of charging coil30. At this time, the conducting wire is bent to a larger degree in agradual manner at the winding end point compared to the winding startpoint. This is done to enhance a force that tries to maintain the shapeof leg portion 32 b.

If the conducting wire is a litz wire, a force that tries to maintainthe shape of charging coil 30 is further enhanced. In the case of a litzwire, since the surface area per wire is large, if an adhesive or thelike is used to fix the shape of charging coil 30, it is easy to fix theshape thereof. In contrast, if the conducting wire is a single wire,because the surface area per conducting wire decreases, the surface areato be adhered decreases and the shape of charging coil 30 is liable tobecome uncoiled.

According to the present embodiment charging coil 30 is formed using aconducting wire having a circular sectional shape, but a conducting wirehaving a square sectional shape may be used as well. In the case ofusing a conducting wire having a circular sectional shape, since gapsarise between adjacent conducting wires, stray capacitance between theconducting wires decreases and the alternating-current resistance ofcharging coil 30 can be suppressed to a small amount.

[Regarding Magnetic Sheet]

Magnetic sheet 10 includes flat portion 12 on which charging coil 30 ismounted, center portion 13 that is substantially the center portion offlat portion 12 and that corresponds to (faces) the inside of the hollowregion of charging coil 30, and slit 11 into which at least a part oftwo leg portions 32 a and 32 b of charging coil 30 is inserted. Slit 11need not be formed as shown in FIGS. 1A and 1B, and is also not limitedto a slit shape that penetrates through magnetic sheet 10, and may beformed in the shape of a non-penetrating recessed portion as shown inFIGS. 2A and 2B. Forming slit 11 in a slit shape facilitates manufactureand makes it possible to securely house the conducting wire. On theother hand, forming slit 11 in the shape of a recessed portion makes itpossible to increase the volume of magnetic sheet 10, and it is therebypossible to improve the L value of charging coil 30 and the transmissionefficiency. Center portion 13 may be formed in a shape that, withrespect to flat portion 12, is any one of a protruding portion shape, aflat shape, a recessed portion shape, and the shape of a through-hole.If center portion 13 is formed as a protruding portion, the magneticflux of charging coil 30 can be strengthened. If center portion 13 isflat, manufacturing is facilitated and charging coil 30 can be easilymounted thereon, and furthermore, a balance can be achieved between theinfluence of aligning magnet 220 and the L value of charging coil 30that is described later. A detailed description with respect to arecessed portion shape and a through-hole is described later.

A Ni—Zn ferrite sheet (sintered body), a Mn—Zn ferrite sheet (sinteredbody), or a Mg—Zn ferrite sheet (sintered body) or the like can be usedas magnetic sheet 10. Magnetic sheet 10 may be configured as a singlelayer, may be configured by stacking a plurality of sheets made of thesame material in the thickness direction, or may be configured bystacking a plurality of different magnetic sheets 10 in the thicknessdirection. It is preferable that, at least, the magnetic permeability ofmagnetic sheet 10 is 250 or more and the saturation magnetic fluxdensity thereof is 350 mT or more.

An amorphous metal can also be used as magnetic sheet 10. The use offerrite sheet as magnetic sheet 10 is advantageous in that thealternating-current resistance of charging coil 30 can be reduced, whilethe use of amorphous metal as magnetic sheet 10 is advantageous in thatthe thickness of charging coil 30 can be reduced.

Magnetic sheet 10 is substantially square with a size of approximately40×40 mm (from 35 mm to 50 mm). In a case where magnetic sheet 10 is asubstantially oblong shape, a short side thereof is 35 mm (from 25 mm to45 mm) and a long side is 45 mm (from 35 mm to 55 mm). The thicknessthereof is 0.43 mm (in practice, between 0.4 mm and 0.55 mm, and athickness between approximately 0.3 mm and 0.7 mm is adequate). It isdesirable to form magnetic sheet 10 in a size that is equal to orgreater than the size of the outer circumferential edge of magnetic body20. Magnetic sheet 10 may be a circular shape, a rectangular shape, apolygonal shape, or a rectangular and polygonal shape having largecurves at four corners.

Slit 11 houses the conducting wire of leg portion 32 a that extend fromwinding start point 32 aa (innermost portion of coil) charging coil 30to the lower end portion of magnetic sheet 10. Thus, slit 11 preventsthe conducting wire from winding start point 32 aa of charging coil 30to leg portion 32 a overlapping in the stacking direction at a planarwinding portion of charging coil 30.

Slit 11 is formed so that one end thereof is substantially perpendicularto an end (edge) of magnetic sheet 10 that intersects therewith, and soas to contact center portion 13 of magnetic sheet 10. In a case wherecharging coil 30 is circular, by forming slit 11 so as to overlap with atangent of center portion 13 (circular), leg portions 32 a and 32 b canbe formed without bending winding start point 32 aa of the conductingwire. In a case where charging coil 30 is a substantially rectangularshape, by forming slit 11 so as to overlap with an extension line of aside of center portion 13 (having a substantially rectangular shape),leg portions 32 a and 32 b can be formed without bending the windingstart portion of the conducting wire. The length of slit 11 depends onthe inner diameter of charging coil 30 and the size of magnetic sheet10. In the present embodiment, the length of slit 11 is betweenapproximately 15 mm and 30 mm.

Slit 11 may also be formed at a portion at which an end (edge) ofmagnetic sheet 10 and center portion 13 are closest to each other. Thatis, when charging coil 30 is circular, slit 11 is formed to beperpendicular to the end (edge) of magnetic sheet 10 and a tangent ofcenter portion 13 (circular), and is formed as a short slit. Further,when charging coil 30 is substantially rectangular, slit 11 is formed tobe perpendicular to an end (edge) of magnetic sheet 10 and a side ofcenter portion 13 (substantially rectangular), and is formed as a shortslit. It is thereby possible to minimize the area in which slit 11 isformed and to improve the transmission efficiency of a wireless powertransmission device. Note that, in this case, the length of slit 11 isapproximately 5 mm to 20 mm. In both of these configurations, the innerside end of slit 11 (slit) is connected to center portion 13.

Next, adverse effects on the magnetic sheet produced by the magnet foralignment described in the foregoing are described. As described above,when the magnet is provided in primary-side wireless charging module 200for alignment, due to the influence of magnet 220, the magneticpermeability of magnetic sheet 10 decreases at a portion that is closeto magnet 220 in particular. Accordingly, the L value of charging coil30 varies significantly between a case where magnet 220 for alignment isprovided in primary-side wireless charging module 200 and a case wheremagnet 220 is not provided. It is therefore necessary to providemagnetic sheet 10 such that the L value of charging coil 30 changes aslittle as possible between a case where magnet 220 is close thereto anda case where magnet 220 is not close thereto.

When the electronic device in which wireless charging module 100 ismounted is a mobile phone, in many cases wireless charging module 100 isdisposed between the case constituting the exterior package of themobile phone and a battery pack located inside the mobile phone, orbetween the case and a substrate located inside the case. In general,since the battery pack is a casing made of aluminum, the battery packadversely affects power transmission. This is because an eddy current isgenerated in the aluminum in a direction that weakens the magnetic fluxgenerated by the coil, and therefore the magnetic flux of the coil isweakened. For this reason, it is necessary to alleviate the influencewith respect to the aluminum by providing magnetic sheet 10 between thealuminum which is the exterior package of the battery pack and chargingcoil 30 disposed on the exterior package thereof. Further, there is apossibility that an electronic component mounted on the substrate willinterfere with power transmission of charging coil 30, and theelectronic component and charging coil 30 will exert adverse effects oneach other. Consequently, it is necessary to provide magnetic sheet 10or a metal film between the substrate and charging coil 30, and suppressthe mutual influences of the substrate and charging coil 30.

In consideration of the above described points, it is important thatmagnetic sheet 10 that is used in wireless charging module 100 have ahigh level of magnetic permeability and a high saturation magnetic fluxdensity so that the L value of charging coil 30 is made as large aspossible. It is sufficient if the magnetic permeability of magneticsheet 10 is 250 or more and the saturation magnetic flux density thereofis 350 mT or more. In the present embodiment, magnetic sheet 10 is aMn—Zn ferrite sintered body having a magnetic permeability between 1,500and 2,500, a saturation magnetic flux density between 400 and 500, and athickness between approximately 400 μm and 700 μm. However, magneticsheet 10 may be made of Ni—Zn ferrite, and favorable power transmissioncan be performed with primary-side wireless charging module 200 as longas the magnetic permeability thereof is 250 or more and the saturationmagnetic flux density is 350 or more.

Charging coil 30 forms an LC resonance circuit through the use of aresonant capacitor. At such time, if the L value of charging coil 30varies significantly between a case where magnet 220 provided inprimary-side wireless charging module 200 is utilized for alignment anda case where magnet 220 is not utilized, a resonance frequency with theresonant capacitor will also vary significantly. Since the resonancefrequency is used for power transmission (charging) between primary-sidewireless charging module 200 and wireless charging module 100, if theresonance frequency varies significantly depending on thepresence/absence of magnet 220, it will not be possible to perform powertransmission correctly. However, by adopting the above describedconfiguration, variations in the resonance frequency that are caused bythe presence/absence of magnet 220 are suppressed, and highly efficientpower transmission is performed in all situations.

A further reduction in thickness is enabled in a case where magneticsheet 10 is a ferrite sheet composed of Mn—Zn ferrite. That is, thefrequency of electromagnetic induction is defined by the standard (WPC)as a frequency between approximately 100 kHz and 200 kHz (for example,120 kHz). A Mn—Zn ferrite sheet provides a high level of efficiency inthis low frequency band. Note that a Ni—Zn ferrite sheet provides a highlevel of efficiency at a high frequency. Accordingly, in the presentembodiment, magnetic sheet 10 that is used for wireless charging forperforming power transmission at a frequency between approximately 100kHz and 200 kHz is constituted by a Mn—Zn ferrite sheet, and magneticbody 20 that is used for NFC communication in which communication isperformed at a frequency of approximately 13.56 MHz is constituted by aNi—Zn ferrite sheet. By using respectively different kinds of ferrite toform magnetic sheet 10 and magnetic body 20 in this manner, magneticsheet 10 and magnetic body 20 can efficiently perform power transmissionand communication, respectively. Further, even when magnetic sheet 10and magnetic body 20 are reduced in thickness and reduced in size,sufficient efficiency can be obtained by magnetic sheet 10 and magneticbody 20, respectively.

A hole may be formed at the center of center portion 13 of magneticsheet 10. Note that, the term “hole” may refer to either of athrough-hole and a recessed portion. The hole may be larger or smallerthan center portion 13, and it is favorable to form a hole that issmaller than center portion 13. That is, when charging coil 30 ismounted on magnetic sheet 10, the hole may be larger or smaller than thehollow portion of charging coil 30. If the hole is smaller than thehollow portion of charging coil 30, all of charging coil 30 will bemounted on magnetic sheet 10.

As described in the foregoing, by configuring wireless charging module100 to be adaptable to both a primary-side (charging-side) wirelesscharging module that uses a magnet and primary-side wireless chargingmodule 200 that does not use a magnet, charging can be performedregardless of the type of primary-side wireless charging module 200,which improves the convenience of the module. There is a demand to makethe L value of charging coil 30 in a case where magnet 220 is providedin primary-side wireless charging module 200 and the L value of chargingcoil 30 in a case where magnet 220 is not provided therein close to eachother, and to also improve both L values. In addition, when magnet 220is disposed in the vicinity of magnetic sheet 10, the magneticpermeability of center portion 13 of magnetic sheet 10 that is in thevicinity of magnet 220 decreases. Therefore, a decrease in the magneticpermeability can be suppressed by providing the hole in center portion13.

FIG. 5 illustrates a relation between an L value of a charging coil in acase where a magnet is provided in the primary-side wireless chargingmodule and a case where a magnet is not provided, and the percentage ofhollowing of the center portion. Note that a percentage of hollowing of100% means that the hole in center portion 13 is a through-hole, and apercentage of hollowing of 0% means that a hole is not provided.Further, a percentage of hollowing of 50% means that, for example, ahole (recessed portion) of a depth of 0.3 mm is provided with respect toa magnetic sheet having a thickness of 0.6 mm.

As shown in FIG. 5, in the case where magnet 220 is not provided inprimary-side wireless charging module 200, the L value decreases as thepercentage of hollowing increases. At such time, although the L valuedecreases very little when the percentage of hollowing is from 0% to75%, the L value decreases significantly when the percentage ofhollowing is between 75% and 100%. In contrast, when magnet 220 isprovided in primary-side wireless charging module 200, the L value risesas the percentage of hollowing increases. This is because the chargingcoil is less liable to be adversely affected by the magnet. At suchtime, the L value gradually rises when the percentage of hollowing isbetween 0% and 75%, and rises significantly when the percentage ofhollowing is between 75% and 100%.

Accordingly, when the percentage of hollowing is between 0% and 75%,while maintaining the L value in a case where magnet 220 is not providedin primary-side wireless charging module 200, the L value in a casewhere magnet 220 is provided in primary-side wireless charging module200 can be increased. Further, when the percentage of hollowing isbetween 75% and 100%, the L value in a case where magnet 220 is notprovided in primary-side wireless charging module 200 and the L value ina case where magnet 220 is provided in primary-side wireless chargingmodule 200 can be brought significantly close to each other. Thegreatest effect is achieved when the percentage of hollowing is between40 and 60%. Magnet 220 and the magnetic sheet can adequately attracteach other when magnet 220 is provided and the L value of a case wheremagnet 220 is provided in primary-side wireless charging module 200 isincreased to 1 μH or more while the L value of a case where no magnet220 is provided in primary-side wireless charging module 200 ismaintained.

[Regarding NFC Coil and Magnetic Body]

The NFC coil will now be described in detail using FIG. 6 to FIGS. 8Aand 8B.

FIG. 6 is a perspective view when the NFC coil and the magnetic bodyaccording to the present embodiment have been assembled. FIG. 7 is anexploded view illustrating the arrangement of the NFC coil and themagnetic body according to the present embodiment.

NFC coil 40 according to the present embodiment that is illustrated inFIG. 6 is an antenna that carries out short-range wireless communicationwhich performs communication by electromagnetic induction using the13.56 MHz frequency, and a sheet antenna is generally used therefor.

As shown in FIG. 6, NFC coil 40 of the present embodiment includesflexible substrate 41 as a conductor arrangement section that is placedso as to envelop the circumference of magnetic body 20 formed of ferriteor the like and which is a coil pattern formed on a support mediummainly constituted by resin. NFC coil 40 is a component that generateslines of magnetic force for NFC communication for performingcommunication with radio communication media such as an unillustrated ICcard or IC tag. While the specific shape of the coil pattern is notillustrated in FIG. 6 and FIG. 7, a coil pattern is formed in whichstraight line with an arrow S is taken as the coil axis. Normally, thecoil pattern and an adjustment pattern that is described later areformed, for example, by copper foil that is formed between two resinlayers, namely, a polyimide film and a cover lay or resist, of flexiblesubstrate 41.

In practice, as shown in FIG. 7, flexible substrate 41 has a shape thatis divided into two parts that sandwich magnetic body 20. In the presentembodiment, for convenience, among the parts of flexible substrate 41that is divided in two, a side that has external connection terminals 42a and 42 b is taken as lower-side flexible substrate (first arrangementsection) 41 a, and the side without external connection terminals 42 aand 42 b is taken as upper-side flexible substrate (second arrangementsection) 41 b. Lower-side flexible substrate 41 a and upper-sideflexible substrate 41 b are joined by soldering. In the presentembodiment, lower-side flexible substrate 41 a and upper-side flexiblesubstrate 41 b are joined at two sides of flexible substrate 41 that aresubstantially parallel with coil axis S. The terms “lower-side” and“upper-side” are assigned to facilitate understanding in FIG. 7, and theupper and lower sides may be reversed at a time of mounting in a deviceas NFC coil 40.

In the present embodiment, the width of upper-side flexible substrate 41b in the direction of coil axis S is set so that magnetic body 20 doesnot protrude. The width is set in this manner so that, particularly in acase in which magnetic body 20 is constituted by ferrite that is easilybroken, broken pieces or residue of magnetic body 20 are prevented fromscattering inside a communication apparatus in which NFC coil 40 ismounted (for example, portable terminal 1 in FIGS. 1A and 1B) andadversely affecting the communication apparatus.

The size of magnetic body 20 is 5 mm×36 mm×0.21 mm. A suitable width inthe longitudinal direction is between 25 mm and 50 mm. As illustrated inFIGS. 1A and 1B, it is preferable to form magnetic body 20 with a largerwidth than the width of magnetic sheet 10 in the same direction. Sinceportions (both ends) that are less susceptible to the influence of (notliable to couple with) charging coil 30 when performing NFCcommunication can thereby be created, the efficiency of NFCcommunication can be improved. Further, a width between 3 and 10 mm inthe short-side direction is sufficient. The width depends on the numberof turns of NFC coil 40. The thickness of magnetic body 20 is preferablythinner than the thickness when magnetic sheet 10 and charging coil 30are stacked, and a thickness between around 0.15 to 1 mm is preferable.

FIGS. 8A and 8B illustrate wiring of the NFC coil in the presentembodiment. FIG. 8A shows lower-side flexible substrate 41 a as seenfrom a contact surface with magnetic body 20, and FIG. 8B showsupper-side flexible substrate 41 b as seen from a contact surfaces withmagnetic body 20. In FIGS. 8A and 8B, the arrow direction of coil axis Sis the near side in the perspective views of flexible substrate 41 shownin FIG. 6 and FIG. 7. Further, in addition to divided pattern 43 a,lower-side flexible substrate 41 a includes external connectionterminals 42 a and 42 b, and in the present embodiment the copper foilof the external connection terminals 42 a and 42 b are also so-called“exposed” and a solder plating process is executed thereon.

A plurality of divided patterns 43 a that serve as a part of NFC coil 40are formed on lower-side flexible substrate 41 a so as to be parallelwith each other and to intersect with coil axis S. Further, onupper-side flexible substrate 41 b, a plurality of divided patterns 43 bthat serve as a part of a coil pattern are also formed so as to beparallel with each other and to intersect with coil axis S. Therespective two ends of the plurality of divided patterns 43 a and 43 bare in a state in which copper foil is “exposed” by respective patternexposing sections 44 a and 44 b and pattern exposing sections 45 a and45 b thereof.

By repeating soldering of the plurality of conductive patterns 43 a and43 b that are divided in a manner that sandwiches magnetic body 20therebetween, a conductive pattern that starts from external connectionterminal 42 a on lower-side flexible substrate 41 a is connected toexternal connection terminal 42 b after going around magnetic body 20.Further, a helical conductive pattern is formed around coil axis S ofmagnetic body 20. The helical conductive pattern is a so-called “coil”pattern, and is capable of generating lines of magnetic force forperforming communication with radio communication media such as IC cardsand IC tags.

In this connection, conductive patterns formed on flexible substrate 41of the present embodiment are not only helical coil patterns. As shownin FIG. 8A, adjustment pattern u that is described in more detailhereunder is provided that is connected to divided pattern t that ispositioned on one side of an outermost edge portion. Adjustment patternu has a plurality of lead-out patterns v in which end parts on one sideare connected to divided pattern t. Adjustment pattern u also hasconnection pattern w that links and is connected with respective endparts on another side that is not connected to divided pattern t oflead-out patterns v, and a protrusion-side end part (end part positionedon the outside of the exterior of magnetic body 20 that is shown by adotted line) of protrusion section lead-out pattern z constituting partof protrusion section y of divided pattern t.

Note that, in the present embodiment, adjustment pattern u is providedonly on the lower-side flexible substrate 41 a side. On the other hand,the plurality of divided patterns 43 a and 43 b forming the coilpatterns shown in FIG. 8A and FIG. 8B are provided in a divided manneron both lower-side flexible substrate 41 a and upper-side flexiblesubstrate 41 b. In addition to adjustment pattern u, external connectionterminals 42 a and 42 b are also provided on lower-side flexiblesubstrate 41 a, and lower-side flexible substrate 41 a has a largerexterior than upper-side flexible substrate 41 b. These parts ofadjustment pattern u (that is, all of connection pattern w and part oflead-out patterns v), part of protrusion section y of divided pattern t,and external connection terminals 42 a and 42 b are arranged atpositions that are further to the outer side than the exterior ofmagnetic body 20 that is shown by a dotted line and upper-side flexiblesubstrate 41 b. In other words, it can be said that these parts ofadjustment pattern u are arranged at positions that are apart from theouter circumference of magnetic body 20 and upper-side flexiblesubstrate 41 b.

Thus, since external connection terminals 42 a and 42 b are not coveredover by magnetic body 20 and upper-side flexible substrate 41 b whenassembly of NFC coil 40 is completed as shown in FIG. 6, as shown inFIGS. 1A and 1B, NFC coil 40 can be connected to an electronic circuitboard that is placed on a surface facing NFC coil 40, and an antennaapparatus can be constructed as a result of such connection.

Further, an adjustment pattern that is not covered by magnetic body 20and upper-side flexible substrate 41 b has at least connection patternw. The inductance of NFC coil 40 shown in FIG. 6 can be adjusted whenassembly of NFC coil 40 is completed by disconnecting either theplurality of lead-out patterns v constituting the adjustment pattern orprotrusion section lead-out pattern z constituting part of protrusionsection y of divided pattern t by trimming or the like.

The inductance of NFC coil 40 is one factor that determines theresonance frequency of the antenna apparatus that is formed when NFCcoil 40 shown in FIGS. 1A and 1B is connected to an electronic circuitboard on which an antenna control section such as a matching circuit ismounted. The inductance of NFC coil 40 having the structure of thepresent embodiment is significantly influenced by variations in the sizeof magnetic body 20. This is because if the size of magnetic body 20varies, the apparent magnetic permeability will also vary.

Thus, since there are individual differences in the inductance of NFCcoil 40 due to variations in the size of magnetic body 20, variationsalso arise in the resonance frequency of an antenna apparatus in whichNFC coil 40 is mounted. By adjusting the resonance frequency within apredetermined range from a center frequency (for example, 13.56 MHz inthe case of RF-ID) defined by communication standards, radiocommunication can be performed with a high probability and quality. Atsuch time, if variations in the inductance of NFC coil 40 alone aredecreased (for example, suppressed to within ±2%), an adjustment rangerequired for adjustment of the resonance frequency of the antennaapparatus in which the relevant NFC coil 40 is mounted can be decreased.Accordingly, the line length of the coil pattern is adjusted in order tosuppress variations in the inductance of NFC coil 40 that areattributable to variations in the size of magnetic body 20.

Trimming of the coil pattern for adjusting the inductance of NFC coil 40is performed at a portion that is further on an outer side than theexterior of magnetic body 20 that is shown by a dotted line amonglead-out patterns v and protrusion section lead-out pattern z in FIG.8A. Since these portions are not covered over by magnetic body 20 andupper-side flexible substrate 41, trimming work can be performed withease.

For example, a difference between the number of turns of a coil patternthat is wound around magnetic body 20 with respect to a case where onlyprotrusion section lead-out pattern z in FIG. 8A is left and lead-outpatterns v are all cut off and a case where only lead-out pattern vadjacent to protrusion section lead-out pattern z is left and the otherportions are all cut off is “c.”

The inductance of NFC coil 40 varies by an amount that corresponds tothat difference.

Note that, in FIG. 8A, protrusion section y that is positioned furtheron the outer side than the exterior of magnetic body 20 need notnecessarily be provided in divided pattern t constituting the coilpattern. However, if protrusion section y is provided, as describedabove, protrusion section lead-out pattern z that constitutes part ofprotrusion section y also contributes to adjustment of the inductance ofthe coil pattern. When divided pattern t that constitutes the coilpattern has protrusion section y that is positioned further on the outerside than the exterior of magnetic body 20, even when NFC coil 40 shownin FIG. 6 is small, it is possible to adequately secure an adjustmentmargin with respect to the inductance of the coil pattern. Further,since protrusion section y in FIG. 8A is a portion that contributes toadjustment of the inductance of the coil pattern together withadjustment pattern u, protrusion section y must be on the flexiblesubstrate that is on the same side as adjustment pattern u is providedon.

FIG. 9 is a conceptual diagram showing an antenna apparatus formed by anelectronic circuit board and an NFC coil that are mounted in a portableterminal according to the present embodiment, and lines of magneticforce generated from the antenna apparatus.

As shown in FIG. 9, the antenna apparatus of the present embodimentincludes magnetic body 20 and NFC coil 40, and an electronic circuitboard that is placed adjacent to NFC coil 40. As is generally known, awiring pattern that connects together terminals of each circuitcomponent mounted on the electronic circuit board is provided on asurface of or inside the electronic circuit board. As a result ofminiaturization achieved by modern circuit integration, in most casesthe electronic circuit board has a plurality of wiring layers.Accordingly, in many cases power supply lines for supplying power toeach circuit component and GND (ground) lines are provided as a separatewiring layer from the aforementioned wiring pattern. Naturally, thesewiring patterns, power supply lines and GND lines are conductors made ofcopper or the like. That is, the electronic circuit board (metal body50) can be regarded as a metal body. When power supply lines and GNDlines are provided as a separate wiring layer as mentioned above, sincethese lines are formed across almost the entire area of the allocatedwiring layer, the electronic circuit board becomes a metal body ofparticularly good quality.

Thus, in the antenna apparatus having NFC coil 40 and the electroniccircuit board that can be regarded as practically a metal body, anopening portion of the coil section of NFC coil 40 is perpendicular tothe electronic circuit board, and NFC coil 40 is placed at an end partof the electronic circuit board. Note that the term “end part of theelectronic circuit board” includes both a case where an end part of NFCcoil 40 projects beyond an outermost edge of the electronic circuitboard and a case where the end part of NFC coil 40 is positioned furtheron the inner side than the outermost edge of the electronic circuitboard.

It is good for NFC coil 40 to be disposed so that the opening portion ofNFC coil 40 is perpendicular to the electronic circuit board and thelongitudinal direction of NFC coil 40 is substantially parallel to anendmost part of the electronic circuit board (NFC coil 40 is disposedalong the endmost part of the electronic circuit board). Therefore, evenwhen, for example, a wireless type IC card is positioned in not onlyregion P but also in region Q, favorable communication can be performed.

That is, since the opening portion of NFC coil 40 is perpendicular tothe electronic circuit board, when a signal is input to NFC coil 40 anda current flows, all of lines of magnetic force M in region Q that aregenerated from NFC coil 40 are in a direction away from NFC coil 40, andlines of magnetic force M pass in only one direction. As a result, acurrent flows through, for example, a wireless type IC card positionedin region Q, and the portable terminal in which the antenna apparatus ofthe present embodiment that includes the electronic circuit board andNFC coil 40 is mounted and the wireless type IC card can conductcommunication.

In addition, in region P also, when a signal is input to NFC coil 40 anda current flows, the direction of lines of magnetic force M in region Pis either one of a direction away from NFC coil 40 and a directiontoward NFC coil 40. This is because lines of magnetic force M generatedfrom NFC coil 40 attenuate in the vicinity of the electronic circuitboard, and therefore axis C of lines of magnetic force M is notperpendicular to the electronic circuit board and is inclined relativethereto. As a result, a current flows through, for example, a wirelesstype IC card positioned in region P, and the portable terminal on whichthe antenna apparatus of the present embodiment that includes theelectronic circuit board and NFC coil 40 is mounted and the wirelesstype IC card can conduct communication.

Note that, in lines of magnetic force M shown in FIG. 9, axis C existsthat connects boundaries of the lines of magnetic force in the directionaway from NFC coil 40 and the lines of magnetic force in the directiontoward NFC coil 40. When a wireless type IC card, for example, is placedin the vicinity of axis C of lines of magnetic force M, the lines ofmagnetic force in both the direction away from the antenna and thedirection toward the antenna act on the wireless type IC card and canceleach other out. As a result, a current does not flow through thewireless type IC card, and communication is not conducted between theportable terminal in which the antenna apparatus of the presentembodiment is mounted and the wireless type IC card.

Next, the reason that axis C of lines of magnetic force M inclines withrespect to the electronic circuit board is described. An eddy currentthat is induced on a surface facing NFC coil 40 of the electroniccircuit board by the lines of magnetic force generated by NFC coil 40produces lines of magnetic force in a perpendicular direction to thesurface that faces NFC coil 40 of the electronic circuit board.Therefore, lines of magnetic force M generated by NFC coil 40 and linesof magnetic force generated from the eddy current induced on the surfacethat faces NFC coil 40 of the electronic circuit board are combined, andlines of magnetic force M generated from NFC coil 40 change in aperpendicular direction in the vicinity of the electronic circuit board.As a result, axis C of lines of magnetic force M inclines to the sidethat is away from the electronic circuit board.

In addition, since NFC coil 40 is placed at an end part of theelectronic circuit board, lines of magnetic force M on the electroniccircuit board side (the right side in FIG. 6) of NFC coil 40 attenuateand lines of magnetic force M on the side away from the electroniccircuit board (the left side in FIG. 6) of NFC coil 40 are strengthenedrelatively. As a result, axis C of lines of magnetic force M is inclinedwith respect to the electronic circuit board. In the configuration ofthe present embodiment, angle a of axis C of lines of magnetic force Minclines at about 40 to 85 degrees with respect to the electroniccircuit board. If NFC coil 40 were not placed at the end part of theelectronic circuit board, the lines of magnetic force in a directionperpendicular to the surface of the electronic circuit board generatedby an eddy current on the surface of the electronic circuit board woulddecrease, and axis C of lines of magnetic force M would remainsubstantially perpendicular to the electronic circuit board. In thatcase, even if communication can be performed in region Q, communicationcannot be conducted in region P.

The end part of NFC coil 40 may be aligned with an end part of theelectronic circuit board, or the end part of NFC coil 40 may projectbeyond the end part of the electronic circuit board. Furthermore, theend part of NFC coil 40 may be placed at a position that is further tothe inner side than the end part of the electronic circuit board.

Thus, a current flowing through the electronic circuit board can beutilized to the maximum by positioning NFC coil 40 at an end part of theelectronic circuit board. Further, the effect of the present inventionis obtained if angle a is approximately 85 degrees, and it is preferablefor angle α to be 80 degrees or less.

[Regarding Configuration of Wireless Charging Module]

Next, the configuration of the wireless charging module will bedescribed. FIGS. 10A and 10B are schematic diagrams of lines of magneticforce generated by the charging coil and the NFC coil of the presentembodiment.

As shown in FIGS. 10A and 10B, the opening portion of NFC coil 40according to the present embodiment is perpendicular to metal body 50,and is placed at an end part of metal body 50.

Note that in some cases NFC coil 40 projects beyond an outermost edge ofmetal body 50 and in some cases NFC coil 40 is located further on theinner side than the outermost edge of metal body 50, and preferably, asdescribed later, a distance between the outer edge of NFC coil 40 andthe outermost edge of metal body 50 is approximately −5 mm to +5 mm.Note that, a negative value of “d” indicates that the outer edge of NFCcoil 40 is located on the inner side relative to the outermost edge ofmetal body 50, and in this case indicates that the outer edge of NFCcoil 40 is located 2 cm on the inner side relative to the outermost edgeof metal body 50. Conversely, a positive value of “d” indicates that theouter edge of NFC coil 40 projects further to the outside than theoutermost edge of metal body 50. Note that, the range from −5 mm to +5mm is due to the width in the short-side direction of magnetic body 20.That is, when the width in the short-side direction of magnetic body 20is taken as “d”, a distance between the outer edge of NFC coil 40 andthe outermost edge of metal body 50 is between approximately −d mm and+d mm, which provides the above described NFC communication favorably.

Next, a case where the NFC coil is a sheet antenna is described forcomparison.

Even when a charging coil for wireless charging and an NFC sheet antennafor NFC communication are in opposite directions, the opening areas facein the same direction. The reason is that a coil is wound in a planarcondition in both the charging coil and the NFC sheet antenna, andfurthermore it is necessary to make the respective opening portionsthereof large to improve communication efficiency and chargingefficiency, and hence the above described configuration is adopted bynecessity in an electronic device for which a reduction in size andreduction in thickness are desired. That is, the reason is that sinceboth the wireless charging module and the NFC sheet antenna that aremounted on the casing of an electronic device that has been reduced insize conduct communication (power transmission) utilizingelectromagnetic induction, the L values are increased by enlarging theopening area of the charging coil and the NFC sheet antenna.

When the directions of communication (axes of the opening portions) aresubstantially the same as described above, both the charging coil andthe NFC sheet antenna may be liable to be influenced by each other. Thatis, magnetic flux for power transmission between the wireless chargingmodule of a charger for wireless charging and a charging coil on acharged-side may be taken by the NFC sheet antenna. Further, the NFCsheet antenna may also receive magnetic flux that the charging coilgenerates when the charging coil receives power. Accordingly, the powertransmission efficiency of the NFC sheet antenna may decrease and thecharging time period may increase. Further, when performing short-rangecommunication with the NFC sheet antenna also, an eddy current may arisein the charging coil in a direction that weakens the magnetic fluxgenerated by the NFC sheet antenna. That is, the thickness of aconducting wire in the charging coil that feeds a large current may belarge in comparison to the NFC sheet antenna that conducts communicationby feeding a small current. Therefore, from the viewpoint of the NFCsheet antenna, the charging coil may be a large metal object, and as faras the NFC sheet antenna is concerned, the eddy current generated in thecharging coil may be of a degree that cannot be ignored. Consequently,the eddy current may adversely affect the efficiency and communicationdistance of short-range communication conducted by the NFC sheetantenna.

In addition, unless the charging coil and the NFC sheet antenna arestacked completely with the respective centers thereof aligned, twolarge planar coils are present on a face of the casing, and from theviewpoint of the wireless charging module on the charger side, it may bedifficult to determine which coil is the charging coil for the side tobe charged. When the alignment accuracy decreases, the powertransmission efficiency may decrease by a corresponding amount.

For example, when performing alignment, a method is available in whichthe wireless charger (primary side) detects the position of the chargingcoil, and a planar coil of the wireless charger (primary side) isautomatically moved to the position of the charging coil. Whiledetection methods which utilize the resonance frequency of the chargingcoil at such time are available, in such a case there is a possibilitythat the resonance frequency of the NFC sheet antenna will be detectedand the planar coil of the wireless charger will be aligned with the NFCsheet antenna.

Further, a method is available in which a large number of coils arearranged in a line in the wireless charger (primary side) to therebyenable charging of a portable terminal device at every place on thecharging surface of the wireless charger (primary side). In this case,the coil (primary side) that is near the NFC sheet antenna may transmita large amount of unnecessary magnetic flux to the NFC sheet antenna. Asa result, there is a risk that wasteful energy consumption or amalfunction will occur.

In addition, in some cases a magnet that is provided on a wirelesscharger (primary side) performs alignment by attracting a magnetic sheetor a magnet that is provided in a hollow portion of a charging coil. Inthis case, since there is a possibility that a magnetic sheet that isused for an NFC sheet antenna will be saturated by the magnet and themagnetic permeability will decrease, the L value of the NFC sheetantenna may sometimes decrease. In such a case there is a risk that thecommunication distance or communication efficiency of the NFC sheetantenna will be reduced.

Therefore, because an opening area of an NFC sheet antenna faces insubstantially the same direction as that of a charging coil andgenerates magnetic flux in substantially the same direction, adverseeffects may be exerted on the communication performance of the NFC sheetantenna and the power transmission performance of the charging coil,irrespective of the alignment method.

In contrast, as shown in FIGS. 10A and 10B, when using NFC coil 40 ofthe present embodiment, since the directions of the opening areas ofcharging coil 30 and NFC coil 40 and the directions of axes A and B ofthe windings of the coils can be made to differ from each other, theabove described problems do not arise, and it is difficult for the coilsto become coupled with each other, and each coil can perform favorablecommunication (power transmission).

That is, as illustrated in FIG. 10B, coil axis A of charging coil 30 isin the vertical direction in the drawing. In contrast, coil axis B ofNFC coil 40 is in the horizontal direction in the drawing. Thus, thecoil axes A and B are in a substantially perpendicular relationship withrespect to each other. As a result, it is difficult for the coils tobecome coupled with each other. Note that it is sufficient if the coilaxes intersect with each other at an angle within a range of around 80to 100 degrees.

In addition, when wireless charging module 100 of the present embodimentis used, it is possible for charging coil 30 and NFC coil 40 to performcommunication in substantially the same direction. This is because NFCcoil 40 behaves in the manner described above using FIG. 9. Note that,in a case where a plurality of NFC coils 40 are provided for thatpurpose, it is good to wind NFC coils 40 so that the magnetic flux ofall NFC coils 40 extend in the same direction (for example, the upwarddirection in FIG. 10B). That is, the two NFC coils 40 in FIG. 10A areeach wound in the clockwise direction as seen from the outside.

Note that since it is preferable for NFC coil 40 to be placed at aposition that is further on the edge side than the center portion sideof metal body 50, it is good to arrange NFC coil 40 on the outer side ofcharging coil 30. As illustrated in FIGS. 10A and 10B, while it is notnecessarily the case that NFC coil 40 must be placed at two placesaround charging coil 30, because axis C of the magnetic flux is causedto incline by metal body 50, it is preferable to arrange NFC coil 40 onboth sides. Further, in FIGS. 10A and 10B, the two NFC coils 40 areconnected in a loop shape so as to surround the circumference ofcharging coil 30.

For example, if charging coil 30 is wound in a substantially oblongshape, and NFC coil 40 is placed along a long side thereof, wirelesscharging module 100 can be reduced in size. Further, if the width in thelongitudinal direction of NFC coil 40 is substantially the same as thewidth in the same direction of charging coil 30, wireless chargingmodule 100 can be reduced in size. In addition, in order to allow axis Cof magnetic flux of NFC coil 40 to incline sufficiently, it ispreferable not to arrange magnetic sheet 10 underneath NFC coil 40.

Next, communication characteristics of the NFC coil in the wirelesscharging module of the present embodiment are described using FIGS. 11Aand 11B to FIGS. 14A and 14B.

FIGS. 11A and 11B are perspective views illustrating a portable terminalincluding the wireless charging module of the present embodiment and,for comparison, a portable terminal including a wireless charging moduleincluding a loop-shaped NFC coil. FIG. 12 illustrates the respectivefrequency characteristics of induced voltages of the two wirelesscharging modules shown in FIGS. 11A and 11B. FIGS. 13A and 13B eachillustrate a magnetic field on a YZ plane of a corresponding one of thetwo wireless charging modules illustrated in FIGS. 11A and 11B. FIGS.14A and 14B each illustrate a magnetic field on a ZX plane of acorresponding one of the two wireless charging modules illustrated inFIGS. 11A and 11B. Note that, for comparison, FIG. 11A, FIG. 13A andFIG. 14A illustrate the case of a wireless charging module that includesa loop-shaped NFC antenna, while FIG. 11B, FIG. 13B and FIG. 14Billustrate the case of the wireless charging module of the presentembodiment.

In FIG. 11A and FIG. 11B, wireless charging module 100 of the presentembodiment and wireless charging module 400 including a loop-shaped NFCantenna are mounted so as to be stacked on battery pack 303. The powertransmission direction of charging coil 30 and the communicationdirection of NFC coil 40 of wireless charging modules 100 and 400,respectively, are the direction of the rear surface of the portableterminal (a side on which a display section such as a liquid crystaldisplay is disposed is assumed to be the front surface).

At such time, as shown in FIG. 12, an induced electromotive force of NFCcoil 40 of wireless charging module 100 is larger than an inducedelectromotive force of the loop-shaped NFC coil of wireless chargingmodule 400. Consequently, the communication efficiency of NFC coil 40 ofwireless charging module 100 is higher than that of loop-shaped NFC coilof wireless charging module 400. Further, as is apparent from FIGS. 13Aand 13B and FIGS. 14A and 14B, a region in which communication can beperformed is wider in the case of NFC coil 40 of wireless chargingmodule 100 than in the case of the loop-shaped NFC coil of wirelesscharging module 400.

At such time, the area of wireless charging module 400 shown in FIG. 11Aand the area of the wireless charging module shown in FIG. 11B aresubstantially the same size (40 mm×40 mm×0.4 mm).

Note that, when the same magnetic sheet 10 and charging coil 30 are usedin wireless charging module 100 and wireless charging module 400, thepower transmission efficiency of charging coil 30 does not changesignificantly. The reason is that charging coil 30 is sufficiently largein comparison to the antenna for NFC communication.

Charging coil 30 is a component for transmitting power during wirelesscharging, and transmits stepped power over an extended time period. Incontrast, communication by NFC coil 40 is performed for a short timeperiod and the amount of power at the time of communication is alsosmall in comparison to charging coil 30. Consequently, a conducting wireconstituting charging coil 30 is thicker than a conducting wireconstituting NFC coil 40, and the number of turns thereof is also morethan the conducting wire constituting NFC coil 40. Consequently, fromthe viewpoint of NFC coil 40, charging coil 30 is a large metal body,and charging coil 30 exerts a large influence on NFC coil 40. Incontrast, from the viewpoint of charging coil 30, NFC coil 40 is small,and NFC coil 40 has little influence on charging coil 30.

Therefore, when the same magnetic sheet 10 and charging coil 30 are usedin wireless charging module 100 and wireless charging module 400,respectively, the power transmission efficiency of charging coil 30 doesnot change significantly, irrespective of the shape of the coil(antenna) for NFC communication.

As described above, by adopting a configuration in which axis A ofcharging coil 30 and axis B of NFC coil 40 intersect with each other,charging coil 30 and the NFC coil can be prevented from interfering witheach other. In particular, mutual interference can be prevented the mostby adopting a configuration in which axis A of charging coil 30 and axisB of NFC coil 40 are substantially orthogonal to each other.

By adopting a configuration in which charging coil 30 is wound in arectangular shape and at least two NFC coils 40 are placed along twofacing sides of rectangular charging coil 30, a region in which NFCcommunication is possible can be extended in a well-balanced manneraround wireless charging module 100. In particular, when mounted in aportable terminal, even if the center of charging coil 30 is placed atthe center side of the portable terminal, the overall center of theplurality of NFC coils 40 can also be located at the center side of theportable terminal. Consequently, it is possible to prevent a situationfrom arising in which a region in which charging is possible and aregion in which NFC communication is possible around the portableterminal are significantly biased toward a particular direction.

Further, arranging NFC coil 40 on the outer side of magnetic sheet 10makes it possible to efficiently perform the communication of NFC coil40. Furthermore, by adopting a configuration in which magnetic sheet 10and magnetic body 20 are constituted by respectively different kinds offerrite, wireless charging and NFC communication can each be performedefficiently.

[Regarding Portable Terminal]

FIGS. 15A to 15E are sectional views that schematically illustrate aportable terminal including the wireless charging module of the presentembodiment. In FIGS. 15A to 15E, the portable terminal includes adisplay section on an upper face side, and a lower face side thereofserves as a communication face. In portable terminal 300 illustrated inFIGS. 15A to 15E, components other than casing 301, substrate 302,battery pack 303, and wireless charging module 100 are not shown, andFIGS. 15A to 15E schematically illustrate arrangement relationshipsbetween casing 301, substrate 302, battery pack 303, and wirelesscharging module 100.

Portable terminal 300 includes, within casing 301, substrate 302 thatperforms control of at least a part of portable terminal 300, batterypack (power holding section) 303 that temporarily stores received power,and wireless charging module 100 that is described above. The displaysection may sometimes include a touch panel function. In such a case, auser operates the portable terminal by performing a touch operation onthe display section. With respect to the orientation of wirelesscharging module 100, naturally magnetic sheet 10 is disposed on thedisplay section side (upper side in FIGS. 15A to 15E), and charging coil30 and NFC coil 40 are disposed so as to face the rear surface side ofcasing 301 (lower side in FIGS. 15A to 15E). It is thereby possible tomake the transmitting direction for wireless charging and also thecommunication direction of the NFC coil the direction of the rearsurface side of casing 301 (lower side in FIGS. 15A to 15E).

In FIG. 15A, among substrate 302, battery pack 303, and wirelesscharging module 100, substrate 302 is disposed furthest on the displaysection side (upper side in FIGS. 15A to 15E), battery pack 303 isdisposed on the rear side of substrate 302, and wireless charging module100 is nearest to the rear surface side of casing 301. At least a partof substrate 302 and a part of battery pack 303 are stacked, and atleast a part of battery pack 303 and wireless charging module 100 arestacked. It is thereby possible to prevent wireless charging module 100and substrate 302 as well as electronic components mounted on substrate302 from exerting adverse effects (for example, interference) on eachother. Further, since battery pack 303 and wireless charging module 100are disposed adjacent to each other, the components can be connectedeasily. In addition, an area for substrate 302, battery pack 303, andwireless charging module 100, in particular, can be adequately secured,and there is a high degree of design freedom. The L values of chargingcoil 30 and NFC coil 40 can be adequately secured.

In FIG. 15B, among substrate 302, battery pack 303, and wirelesscharging module 100, substrate 302 is disposed furthest on the displaysection side (upper side in FIGS. 15A to 15E), and battery pack 303 andwireless charging module 100 are disposed in parallel on the rear sideof substrate 302. That is, battery pack 303 and wireless charging module100 are not stacked, and are disposed in parallel in the transversedirection in FIGS. 15A to 15E. At least a part of substrate 302 andbattery pack 303 are stacked, and at least a part of substrate 302 andwireless charging module 100 are stacked. Thus, since battery pack 303and wireless charging module 100 are not stacked, casing 301 can be madethinner. In addition, an area for substrate 302, battery pack 303, andwireless charging module 100, in particular, can be adequately secured,and there is a high degree of design freedom. The L values of chargingcoil 30 and NFC coil 40 can be adequately secured.

In FIG. 15C, among substrate 302, battery pack 303, and wirelesscharging module 100, substrate 302 and battery pack 303 are disposedfurthest on the display section side (upper side in FIGS. 15A to 15E),and wireless charging module 100 is disposed on the rear side of batterypack 303. That is, battery pack 303 and substrate 302 are not stacked,and are disposed in parallel in the transverse direction in FIGS. 15A to15E. At least a part of battery pack 303 and a part of wireless chargingmodule 100 are stacked. Thus, since battery pack 303 and substrate 302are not stacked, casing 301 can be made thinner. Further, since batterypack 303 and wireless charging module 100 are stacked and thus batterypack 303 and wireless charging module 100 are disposed adjacent to eachother, these components can be connected easily. In addition, an areafor substrate 302, battery pack 303, and wireless charging module 100can be adequately secured, and the L values of charging coil 30 and NFCcoil 40 can be adequately secured.

In FIG. 15D, among substrate 302, battery pack 303, and wirelesscharging module 100, substrate 302 and battery pack 303 are disposedfurthest on the display section side (upper side in FIGS. 15A to 15E),and wireless charging module 100 is disposed on the rear side ofsubstrate 302. That is, battery pack 303 and substrate 302 are notstacked, and are disposed in parallel in the transverse direction inFIGS. 15A to 15E. At least a part of substrate 302 and a part ofwireless charging module 100 are stacked. Thus, since battery pack 303and substrate 302 are not stacked, casing 301 can be made thinner. Ingeneral, battery pack 303 is the thickest among substrate 302, batterypack 303, and wireless charging module 100. Therefore, rather thanstacking the battery pack and another component, casing 301 can be madethin by stacking substrate 302 and wireless charging module 100.Further, an area for substrate 302, battery pack 303, and wirelesscharging module 100 can be adequately secured, and the L values ofcharging coil 30 and NFC coil 40 can be adequately secured.

In FIG. 15E, substrate 302, battery pack 303, and wireless chargingmodule 100 are disposed on the display section side (upper side in FIGS.15A to 15E). That is, substrate 302, battery pack 303, and wirelesscharging module 100 are not stacked with respect to each other at all,and are disposed in parallel in the transverse direction in FIGS. 15A to15E. Thus casing 301 can be made with the smallest thickness among theconfigurations illustrated in FIGS. 15A to 15E.

The disclosure of the specification, drawings, and abstract included inJapanese Patent Application No. 2012-032317 filed on Feb. 17, 2012 isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is useful for various kinds of electronic devicessuch as a portable terminal including the wireless charging module thatincludes a wireless charging module and an NFC antenna, in particular,portable devices such as a mobile phone, a portable audio device, apersonal computer, a digital camera, and a video camera.

REFERENCE SIGNS LIST

100 Wireless charging module

10 Magnetic sheet

11 Slit

12 Flat portion

13 Center portion

20 Magnetic body

30 Charging coil

31 a, 31 b, 31 c, 31 d Corner portion

32 a, 32 b Leg portion

33 Inner portion

40 NFC coil

50 Metal body

200 Primary-side wireless charging module

210 Primary-side coil

220 Magnet

300 Portable terminal

301 Casing

302 Substrate

303 Battery pack

1. A mobile terminal having substantially planar front and back surfacesand comprising: a wireless charging module including a charging coilformed of a wound conducting wire and having a substantially planarshape; a battery pack having a substantially planar shape and configuredto store power from the wireless charging module; a circuit boardsubstrate configured to control operation of the mobile terminal; and adisplay placed such that the circuit board is interposed between thedisplay and the wireless charging coil along a thickness directionorthogonal to the front and back surfaces of the mobile terminal,wherein, the circuit board substrate does not overlap with the batterypack along the thickness direction of the mobile terminal.
 2. The mobileterminal according to claim 1, wherein the charging coil is formed in anoval shape or a circular shape.
 3. The mobile terminal according toclaim 1, wherein the charging coil is formed to define a hollow portionsurrounded by the wound conducting wire.
 4. The mobile terminalaccording to claim 3, wherein the hollow portion has an oval shape or acircular shape.
 5. The mobile terminal according to claim 4, wherein thelargest linear dimension of the hollow portion is greater than 15.5 mm.6. The mobile terminal according to claim 3, further comprising amagnetic sheet on which the charging coil is mounted.
 7. The mobileterminal according to claim 6, wherein the magnetic sheet has a raisedportion that faces the hollow portion of the charging coil.
 8. Themobile terminal according to claim 6, wherein the magnetic sheetincludes a slit in which two end portions of the conducting wire arereceived.
 9. The mobile terminal according to claim 6, wherein acombined thickness of the charging coil and the magnetic sheet isbetween 0.6 mm and 1.0 mm.
 10. The mobile terminal according to claim 1,wherein the wireless charging module overlaps with the circuit boardsubstrate.
 11. The mobile terminal according to claim 1, wherein thewireless charging module overlaps with the battery pack.
 12. The mobileterminal according to claim 1, wherein the wireless charging moduleoverlaps with both the circuit board substrate and the battery pack. 13.The mobile terminal according to claim 1, wherein the substantiallyplanar front surface is at least partially provided by the display, andthe wireless charging coil is configured to perform wireless chargingvia the substantially planar back surface.